/****************************************************************************
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 ** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
 ** Contact: http://www.qt-project.org/legal
 **
 ** This file is part of the examples of the Qt Toolkit.
 **
 ** $QT_BEGIN_LICENSE:BSD$
 ** You may use this file under the terms of the BSD license as follows:
 **
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 ** modification, are permitted provided that the following conditions are
 ** met:
 **   * Redistributions of source code must retain the above copyright
 **     notice, this list of conditions and the following disclaimer.
 **   * Redistributions in binary form must reproduce the above copyright
 **     notice, this list of conditions and the following disclaimer in
 **     the documentation and/or other materials provided with the
 **     distribution.
 **   * Neither the name of Digia Plc and its Subsidiary(-ies) nor the names
 **     of its contributors may be used to endorse or promote products derived
 **     from this software without specific prior written permission.
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 ****************************************************************************/

#include <QtGui>

#include "QCodeEditor.h"

class LineNumberArea : public QWidget
{
  public:
    LineNumberArea(QCodeEditor* editor)
      : QWidget(editor)
    {
        codeEditor = editor;
    }

    QSize sizeHint() const override { return { codeEditor->lineNumberAreaWidth(), 0 }; }

  protected:
    void paintEvent(QPaintEvent* event) override { codeEditor->lineNumberAreaPaintEvent(event); }

  private:
    QCodeEditor* codeEditor;
};

QCodeEditor::QCodeEditor(QWidget* parent)
  : QPlainTextEdit(parent)
{
    m_lineNumberArea = new LineNumberArea(this);

    connect(this, SIGNAL(blockCountChanged(int)), this, SLOT(updateLineNumberAreaWidth(int)));
    connect(this, SIGNAL(updateRequest(QRect, int)), this, SLOT(updateLineNumberArea(QRect, int)));
    connect(this, SIGNAL(cursorPositionChanged()), this, SLOT(highlightCurrentLine()));

    updateLineNumberAreaWidth(0);
    highlightCurrentLine();
}

int
QCodeEditor::lineNumberAreaWidth() const
{
    int digits = 1;
    int max = qMax(1, blockCount());
    while (max >= 10) {
        max /= 10;
        ++digits;
    }

    return 3 + fontMetrics().horizontalAdvance(QLatin1Char('9')) * digits;
}

void
QCodeEditor::updateLineNumberAreaWidth(int /* newBlockCount */)
{
    setViewportMargins(lineNumberAreaWidth(), 0, 0, 0);
}

void
QCodeEditor::updateLineNumberArea(QRect rect, int dy)
{
    if (dy)
        m_lineNumberArea->scroll(0, dy);
    else
        m_lineNumberArea->update(0, rect.y(), m_lineNumberArea->width(), rect.height());

    if (rect.contains(viewport()->rect()))
        updateLineNumberAreaWidth(0);
}

void
QCodeEditor::resizeEvent(QResizeEvent* e)
{
    QPlainTextEdit::resizeEvent(e);

    const QRect cr = contentsRect();
    m_lineNumberArea->setGeometry(QRect(cr.left(), cr.top(), lineNumberAreaWidth(), cr.height()));
}

void
QCodeEditor::highlightCurrentLine()
{
    QList<QTextEdit::ExtraSelection> extraSelections;

    if (!isReadOnly()) {
        QTextEdit::ExtraSelection selection;

        QColor lineColor = QColor(Qt::yellow).lighter(160);

        selection.format.setBackground(lineColor);
        selection.format.setProperty(QTextFormat::FullWidthSelection, true);
        selection.cursor = textCursor();
        selection.cursor.clearSelection();
        extraSelections.append(selection);
    }

    setExtraSelections(extraSelections);
}

void
QCodeEditor::lineNumberAreaPaintEvent(QPaintEvent* event)
{
    QPainter painter(m_lineNumberArea);
    painter.fillRect(event->rect(), QColor(232, 233, 232));

    QTextBlock block = firstVisibleBlock();
    int blockNumber = block.blockNumber();
    int top = (int)blockBoundingGeometry(block).translated(contentOffset()).top();
    int bottom = top + (int)blockBoundingRect(block).height();

    while (block.isValid() && top <= event->rect().bottom()) {
        if (block.isVisible() && bottom >= event->rect().top()) {
            QString number = QString::number(blockNumber + 1);
            painter.setPen(QColor(177, 178, 177));
            painter.drawText(
              0, top, m_lineNumberArea->width(), fontMetrics().height(), Qt::AlignRight, number);
        }

        block = block.next();
        top = bottom;
        bottom = top + (int)blockBoundingRect(block).height();
        ++blockNumber;
    }
}
